if you are compiling the latest testing firmware i will test it.
i was starting to compile it by myself with the linked patch but didnt get a working firmware till now.
i was not sure how to git clone the test branch and downloaded it manually now.
i was not sure if git clone -b nbg7815-test https://github.com/asvio/openwrt.git is actually doing the job - and for compiling i am using the docker image https://github.com/mwarning/docker-openwrt-build-env
in this posting Zyxel Armor Z2 (NBG6817) - 3GB extroot on 19.07 - #13 by utrumo he is writing one should activate block-mound and blockd - in your config is only block-mount activated, maybe you can try installing it and see if it makes a difference in your third firmware release.